Study shows revaccination with existing TB vaccine prevents TB infection later in life

Getting revaccinated later in life with the same vaccine given to infants to prevent tuberculosis may provide additional protection after the original vaccine loses efficacy, researchers at the 5th Global Forum on TB Vaccines in New Delhi, India, revealed. The Bacillus Calmette–Guérin, or BCG, vaccine is partially effective against preventing TB infection in children for 10-15 years, researchers said, but until now a second dose of BCG has not been shown to prevent TB infection in adolescents or adults.

The study – conducted by Aeras, Sanofi Pasteur, the South African Tuberculosis Vaccine Initiative, and the Desmond Tutu HIV Foundation – examined whether revaccinating healthy adolescents at high risk of becoming infected with TB in Cape Town, South Africa, with BCG or a novel subunit vaccine reduced the risk of becoming infected with TB. Compared to participants in the placebo arm, adolescents who received BCG showed significantly fewer sustained TB infections at the end of the study period, researchers said.

While the subunit vaccine, which contains specific pieces of the TB-causing bacteria to stimulate a response in the immune system, did not show reduced sustained infections at a statistically significant level, it is the first subunit vaccine that has shown any protection against TB infection, Mark Hatherill, director of the South African TB Vaccine Initiative, said.

“We believe the results from this novel trial design will provide significant scientific benefit to the field in understanding TB infection, and based on this positive signal, we look forward to testing the potential of such vaccines to prevent TB disease among uninfected adolescents in a larger, more traditional prevention-of-disease clinical trial,” Hatherill said in a release.

“We believe the results are important and warrant further investigation into other subunit vaccines and a reevaluation of BCG revaccination as a potential strategy to prevent TB in high-incidence countries,” said Linda-Gail Bekker lead investigator and president of the International AIDS Society. “An effective TB vaccine remains an urgent global goal,” she said.